In order to access the performance of buildings under daylight, scaled models are usually used for the purpose of research and practice. The reason for using scaled models is mainly due to convenience, cost effectiveness, proof-of-concept and time saving. Recently, the emergence of research into energy efficient Green Buildings has facilitated new ideas in areas of lighting power grid (electricity), BMS (Building Management System), ACMV (Air Conditioning and Mechanical Ventilation), etc. However, over the past ten years, studies have found that there exist performance discrepancies between results gathered from scaled models and actual implementation, resulting in over estimation of the performances. This over estimation of between 30% to 105% in favor of the scaled model can be attributed to model details/replication, surface reflectance, light leakages, fenestration details, photometric properties, luxmeters sensing aperture size, and window transmittance.
To overcome the limitation of the scaled models, actual 1:1 size models should be used under actual outdoor exposure. This solution is the most direct in implementation and at the same time, provides an exact representation of the actual deployment. Unfortunately, the associated behaviors between Earth and Sun is not a constant one. The solar spectrum, geometry of solar radiation, and intensity varies depending on diurnal and annual variation, location, atmospheric conditions, and terrestrial conditions. With these in consideration, studies conducted outdoors are limited by the location, weather, and seasons.
It is therefore necessary to have a man-made environment, where all variables can be controlled deterministically. To access the performance of daylighting on buildings, an indoor testing facility with controlled emulation of the daylight would provide a solution to address the above issues, wherein an indoor test-bed may be shielded from external elements to provide a predictable 24/7 testing environment for research and practice.
Efforts have been made to enhance the light artificially produced by either conventional fluorescent or newer LEDs (light-emitting devices) in terms of color, color temperature, and brightness by using a combination of different types of lighting sources, such as different color LEDs, to produce light of different colors.
Attempts have been made to improve white light artificially produced for industry and commercial applications, such as car show rooms, jewellery shops, clothing stores and offices. The main concern is to produce light with high Color Rendering Index (CRI) so that objects viewed under these lights can reproduce the natural colors when viewed under the Sun.
Other attempts have also be made to use different colors of white light (Correlated Color Temperature, CCT) to improve and influence the behavior of humans, for example, to improve the mental state of office workers or reduce the recovery time of patients in the hospitals.
In order to achieve the desired results, different light sources (e.g., LEDs), typically 3 to 6 types of LEDs are arranged in a manner, typically in circular form or in strip form, to mix the required colors or white color temperature. Some of the proposed light fixtures are in modular form, which can be scaled up to produce a larger light source. Each module can be controlled independently by either changing the current and/or voltages to the light sources or through some digital drivers.
Despite the recognition of the need for variable CCT and intensity of light sources for use in various applications, it is not revealed how the uniformity, CCT, and intensity can be achieved in a single device. In addition, the need of having a lighting device that can emulate the daylight for research purposes in buildings and also for design purposes in architectural projects is not indicated.
Therefore, there is a need for a device that can emulate the daylight in terms of CCT and intensity relating to the diurnal, seasonal and location parameters. There is also a need for a device which is large enough to project the required light onto a surface of an actual “life size” test bed uniformly.